Compositions for reducing resist consumption of extreme ultraviolet metallic type resist

ABSTRACT

A method for reducing resist consumption (RRC) is provided. The method includes treating a surface of a substrate using a RRC composition and forming a photoresist layer comprising a metal-containing material on the RRC composition treated surface. The RRC composition includes a solvent and an acid or a base. The solvent has a dispersion parameter between 10 and 25. The acid has an acid dissociation constant between -20 and 6.8. The base having an acid dissociation constant between 7.2 and 45.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designhave produced generations of ICs where each generation has smaller andmore complex circuits than the previous generation. In the course of ICevolution, functional density (i.e., the number of interconnecteddevices per chip area) has generally increased while geometry size(i.e., the smallest component (or line) that can be created using afabrication process) has decreased. This scaling down process generallyprovides benefits by increasing production efficiency and loweringassociated costs. Such scaling down has also increased the complexity ofprocessing and manufacturing ICs.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a block diagram of a spin coater system for coating asubstrate, in accordance with some embodiments.

FIG. 2 is a flow chart of a method for fabricating a semiconductorstructure, in accordance with some embodiments.

FIGS. 3A-3F are cross-sectional views of a semiconductor structurefabricated using the method of FIG. 2 , in accordance with someembodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components, values, operations, materials,arrangements, or the like, are described below to simplify the presentdisclosure. These are, of course, merely examples and are not intendedto be limiting. Other components, values, operations, materials,arrangements, or the like, are contemplated. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The system may be otherwise oriented (rotated 90 degrees orat other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

IC fabrication uses one or more photolithography processes to transfergeometric patterns to a film or substrate. Geometric shapes and patternson a semiconductor make up the complex structures that allow thedopants, electrical properties and wires to complete a circuit andfulfill a technological purpose. In a photolithography process, aphotoresist is applied as a thin film to a substrate, and subsequentlyexposed through a photomask. The photomask contains clear and opaquefeatures that define a pattern which is to be created in the photoresistlayer. Areas in the photoresist exposed to light transmitted through thephotomask are made either soluble or insoluble in a specific type ofsolution known as a developer. In the case when the exposed regions aresoluble, a positive image of the photomask is produced in thephotoresist and this type of photoresist is called a positivephotoresist. On the other hand, if the unexposed areas are dissolved bythe developer, a negative image results in the photoresist and this typeof photoresist is called a negative photoresist. After developing, theareas no longer covered by photoresist are removed by etching, therebyreplicating the mask pattern in the substrate. To ensure that theprojected image is properly exposed onto the substrate, it is importantthat the photoresist layer is smooth and coats the substrate completelyand uniformly. The cost of photoresist is a significant material cost insemiconductor fabrication. Reducing the amount of photoresist used toreduce the fabrication costs is also important.

Spin coating is the most common method used when coating a substratewith photoresist. In order to improve the resist coating thicknessuniformity and to reduce the resist dispense volume, prior to applyingthe photoresist, the surface of the substrate is treated with a solvent,so called reducing resist consumption (RRC) solvent. The RRC solventprovides a clean and hydrophobic surface which boosts the adhesion ofthe photoresist to the substrate surface. The RRC solvent may typicallybe OK73, which includes about 70% propylene glycol monomethylether(PGME) and about 30% Propylene glycol monomethylether acetate (PGMEA).

As semiconductor device sizes continue to shrink, for example below 20nanometer nodes, traditional lithography technologies have opticalrestrictions, which leads to resolution issues and may not achieve thedesired lithography performance. In comparison, extreme ultraviolet(EUV) lithography using EUV radiation around 13.5 nm can achieve muchsmaller device sizes. However, conventional polymer photoresists sufferfrom low absorption efficiency to EUV light source, long exposure timesare thus needed, resulting in low throughput. One solution to thisproblem is to use metallic photoresists containing metals having highEUV absorbance improved EUV sensitivity. However, compared to organicphotoresists, metallic photoresists tend to be relatively hydrophilic,OK73 thus is no longer suitable as the RRC solvent due to the solubilitymismatch between OK73 and the metallic photoresists. Therefore, theresist coating suffers from precipitation of the photoresist materialand/or poor resist thickness uniformity, leading to various patterningissues, such as increased line width roughness (LWR) and CDnon-uniformity. These patterning defects cause semiconductor fabricationproblems and/or degrade semiconductor device performance. Therefore,there is a need for a RRC composition to reduce the resist dispenseamount and to improve the coating thickness uniformity of metallicphotoresists, which leads to an increase in EUV lithography performanceand a decrease in the fabrication cost.

In embodiments of the present disclosure, a composition for reducingresist consumption (RRC) and improving coating thickness uniformity of ametal-containing photoresist ((also referred to as RRC composition) isprovided. The RRC composition thus helps to improve the EUV lithographyperformance such as improved line width roughness (LWR) and reduceddefect counts. As a result, the final yield is improved and thefabrication cost is reduced.

In some embodiments, the RRC composition includes an organic solvent andan acid or a base.

The organic solvent is selected based on the Hansen solubilityparameters, dispersion parameter (δ_(d)), polarity parameter (δ_(p)),and hydrogen bonding parameter (δ_(h)). The polarity parameter (δ_(p))is the energy from dipolar intermolecular force between the molecules.The hydrogen bonding parameter (δ_(h)) is the energy from hydrogen bondsbetween the molecules. The three parameter, δ_(d), δ_(p), and δ_(h), canbe considered as coordinates for a point in three dimensions, known asthe Hansen space. The nearer two molecules are in Hansen space, the morelikely they are to dissolve into each other. In some embodiments, theorganic solvent has a dispersion parameter (δ_(d)) in between 10 and 25(10<δ_(d)<25), a polarity parameter (δ_(p)) between 3 and 25(3<δ_(p)<25), and a hydrogen bonding parameter (δ_(h)) between 4 and 30(4<δ_(h)<30).

The organic solvents having the desired Hansen solubility parameters inthe above ranges include, but are not limited to, propylene glycolmethyl ether (PGME), propylene glycol ethyl ether (PGEE),y-butyrolactone (GBL), cyclohexanone (CHN), ethyl lactate (EL), methylisobutyl carbinol (MIBC), propylene glycol monomethyl ether acetate(PGMEA), methanol, ethanol, propanol, n-butanol, acetone, dimethylfuran,acetonitrile, isopropyl alcohol (IPA), tetrahydrofuran (THF), aceticacid, diacetone alcohol (DAA), and combinations thereof.

In some embodiments, the acid has an acid dissociation constant, pKa,between 6.8 and 20 (6.8 <pKa <20). In some embodiments , the acid is anorganic acid including, but not limited to, ethanedioic acid, methanoicacid, 2-hydroxypropanoic acid, 2-hydroxybutanedioic acid, citric acid,uric acid, trifluoromethanesulfonic acid, benzenesulfonic acid,ethanesulfonic acid, methanesulfonic acid, acetic acid, oxalic acid,maleic acid, carbonic acid, oxoethanoic acid, 2-hydroxy ethanoic acid,propanedioic acid, butanedioic acid, 3-oxobutanoic acid,hydroxylamine-o-sulfonic acid, formamidine sulfinic acid, methylsulfamicacid, sulfoacetic acid, 1,1,2,2-tetrafluoroethanesulfonic acid,1,3-propanedisulfonic acid, nonafluorobutane-1-sulfonic acid,5-sulfosalicylic acid, trichloroacetic acid, and combinations thereof.In some embodiments, the acid is an inorganic acid including, but notlimited to, nitric acid (HNO₃), sulfuric acid (H₂SO₄), hydrochloric acid(HCl), hydrobromic acid (HBr), phosphoric acid (H₃PO₄), and combinationsthereof.

In some embodiments, the base has a pKa between 7.2 and 45 (7.2<pKa<45).In some embodiments , the base is an organic base including, but notlimited to, monoethanolamine, monoisopropanolamine,2-amino-2-methyl-1-propanol, 1H-benzotriazole, 1,2,4 - triazole,1,8-diazabicycloundec-7-ene, 1,5-Diazabicyclo[4.3.0]non-5-ene,tetrabutylammonium hydroxide, tetramethylammonium hydroxide (TMAH),tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide, andcombinations thereof. In some embodiments, the base is an inorganic baseincluding, but not limited to, ammonia (NH₃), ammonium hydroxide,ammonium sulfamate, ammonium carbamate, sodium hydroxide (NaOH),potassium hydroxide (KOH), and combinations thereof.

In some embodiments, the concentration of the acid or base ranges from0.001 wt. % to 30 wt. % based on the total weight of the RRCcomposition. In some embodiments, the concentration of the acid or baseranges from 0.1 wt. % to 20 wt. % based on the total weight of the RRCcomposition

In some embodiments, the RRC composition further includes a chelatingagent. In some embodiments, the chelating agent includes, but is notlimited to, ethylenediaminetetraacetic acid (EDTA),ethylenediamine-N,N′-disuccinic acid (EDDS),diethylenetriaminepentaacetic acid (DTPA), polyaspartic acid,trans-1,2-cyclohexanediamine-N,N,N, N′-tetraacetic acid monohydrate,ethylenediamine, and combinations thereof. The RRC composition mayinclude 30 wt. % or less of chelating agent. In some embodiments, theconcentration of the chelating agent ranges from 0.001 wt. % to 30 wt. %based on the total weight of the RRC composition. In some embodiments,the concentration of the chelating agent ranges from 0.01 wt. % to 20wt. % based on the total weight of the RRC composition.

In some embodiments, the RRC composition further includes a surfactantto increase the solubility and reduce the surface tension of thesubstrate. In some embodiments, the surfactant includes, but not limitedto, alkylbenzenesulfonates, lignin sulfonates, fatty alcoholethoxylates, and alkylphenol ethoxylates. In some embodiments , thesurfactant is selected from the group consisting of sodium stearate ,4-(5-dodecyl) benzenesulfonate, ammonium lauryl sulfate, sodium laurylsulfate, sodium laureth sulfate, sodium myreth sulfate, dioctyl sodiumsulfosuccinate, perfluorooctanesulfonate, perfluorobutanesulfonate,alkyl-aryl ether phosphate, alkyl ether phosphates, sodium lauroylsarcosinate , perfluoronononanoate , perfluorooctanoate, octenidinedihydrochloride, cetrimonium bromide, cetylpyridinium chloride,benzalkonium chloride, benzethonium chloride, nethyldioctadecylammoniumchloride, dioctadecyldimethylammonium bromide, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, cocamidopropyl hydroxysultaine,cocamidopropyl betaine, phospholipidsphosphatidylserine,phosphatidylethanolamine, phosphatidylcholine, sphingomyelins,octaethylene glycol monodecyl ether, pentaethylene glycol monodecylether, polyethoxylated tallow amine, cocamide monoethanolamine, cocamidediethanolamine, glycerol monostearate, glycerol monolaurate, sorbitanmonolaurate, sorbitan monostearate, sorbitan tristearate, andcombinations thereof. In some embodiments, the surfactant ispolyethylene oxide or polypropylene oxide.

The RRC composition may include 5 wt. % or less of surfactant. In someembodiments, the concentration of the surfactant ranges from 0.1 wt. %to 5 wt. % based on the total weight of the RRC composition.

In some embodiments, the RRC composition further includes an aqueoussolvent. As used herein, the term “aqueous solvent” denotes a liquidthat is water miscible (miscibility in water of greater than 50% byweight at 25° C. and atmospheric pressure). In some embodiments, theaqueous solvent includes lower monoalcohols containing from 1 to 5carbon atoms, such as ethanol and isopropanol, glycols containing from 2to 8 carbon atoms, such as ethylene glycol, propylene glycol,1,3-butylene glycol and dipropylene glycol, C3-C4 ketones and C2-C4aldehydes. The RRC composition may include 20 wt. % or less of aqueoussolvent. In some embodiments, the concentration of the aqueous solventranges from 0.001 wt. % to 20 wt. % based on the total weight of the RRCcomposition. In some embodiments, the concentration of the aqueoussolvent ranges from 0.1 wt. % to 10 wt. % based on the total weight ofthe RRC composition.

In some embodiments, the RRC composition further includes water. The RRCcomposition may include 20 wt. % or less of water. In some embodiments,the concentration of water ranges from 0.1 wt. % to 20 wt. % based onthe total weight of the RRC composition. In some embodiments, theconcentration of water ranges from 10 wt. % to 20 wt. % based on thetotal weight of the RRC composition.

In some embodiments, the RRC composition further includes a high boilingpoint solvent with a boiling point greater than 150° C. In someembodiments, the high boiling point solvent that can be employed in thepresent disclosure includes, but is not limited to, CHAX, dipropyleneglycol dimethyl ether (DMM), propylene glycol diacetate (PGDA),dipropylene glycol methyl n-propyl ether (DPMNP), dipropylene glycolmethyl ether acetate (DPMA), 1,4-butanediol diacrylate (1,4-BDDA),1,3-butanediol diacetate (1,3-BGDA), 1,6-hexanediol diacrylate(1,6-HDDA), tripropylene glycol monomethyl ether (TPM), 1,3-propanediol,propylene glycol, 1-methoxy-2-(2-propoxypropoxy)propane, hexane-1,6-diyldiacetate, butane-1,4-diyl diacetate, propane-1,2-diyl diacetate,2-methoxy-1-((1-methoxypropan-2-yl)oxy)propane,1-((1-methoxypropan-2-yl)oxy)propan-2-yl acetate, butane-1,2,4-triol,2-(2-(2-methoxypropoxy)propoxy)propan-1-ol, and combinations thereof.The RRC composition may include 35 wt. % or less of high boiling pointsolvent. In some embodiments, the concentration of the high boilingpoint solvent ranges from 0.1 wt. % to 35 wt. % based on the totalweight of the RRC composition.

FIG. 1 is a block diagram of a spin coater system 100 for coating asubstrate 102 with a thin film, in accordance with some embodiments ofpresent disclosure. It is noted that the system 100 is merely anexample, and is not intended to limit the present disclosure.Accordingly, it is understood that additional functional blocks may beprovided in or coupled to the system 100 of FIG. 1 , and that some otherfunctional blocks may only be briefly described herein.

In the illustrated embodiment, the spin coater system 100 is to deposita uniform thin film to a surface of a substrate 102 using centrifugalforce. In some embodiments, the thin film comprises a RRC composition ora photoresist. In some embodiments, the system 100 comprises a chuck 104for securing the substrate 102 firmly without deflection while operatingat a very high rotational speed. In some embodiments, the chuck 104 hasa mass that allows for instantaneous direction and speed change withprecise acceleration and deceleration control. In some embodiments, thechuck 104 is a vacuum chuck. In some embodiments, the vacuum chuck 104comprises a low-profile, O-ring seal for high-performance vacuum seal.In some other embodiments, the chuck 104 comprises an edge-grip chuckfor substrates that are sensitive to vacuum contact. In someembodiments, the chuck 104 is attached to a motor (not shown) which isconfigured to provide precise speed control.

In some embodiments, the system 100 comprises a holder 106 with at leastone nozzle 108/110 for dispensing a coating 112 onto the substrate 102.In the illustrated embodiment, the system 100 comprises two nozzles 108and 110 with a first nozzle 108 for dispensing a RRC composition of thepresent disclosure from a RRC composition source 114 and a second nozzle110 for dispensing a photoresist from a photoresist source 116. In someembodiments, the RRC composition source 114 and the photoresist source116 each comprise a respective pump (not shown) for injecting thematerials into the respective nozzles 108/110. In some embodiments, theRRC composition and photoresist are both directed through a singlenozzle and injected by a single pump.

In some embodiments, the pump attached to the RRC composition source 114and photoresist source 116 is further coupled to a controller 120 tocontrol the time and rate of the dispensing of the RRC composition andthe photoresist. In some embodiments, the controller 120 is furthercoupled to the motor coupled to the chuck 104 so as to control thespeed, acceleration/deceleration, and spinning time of the chuck 104. Insome embodiments, the dispensing of the RRC composition and thephotoresist and the spinning of the chuck are synchronized andautomatically controlled by the controller 120.

In some embodiments, the controller 120 is a representative device andmay comprise a processor, a memory, an input/output interface, acommunications interface, and a system bus. The processor may compriseany processing circuitry operative to control the operations andperformance of the controller 120. In various aspects, the processor maybe implemented as a general purpose processor, a chip multiprocessor(CMP), a dedicated processor, an embedded processor, a digital signalprocessor (DSP), a network processor, an input/output (I/O) processor, amedia access control (MAC) processor, a radio baseband processor, aco-processor, a microprocessor such as a complex instruction setcomputer (CISC) microprocessor, a reduced instruction set computing(RISC) microprocessor, and/or a very long instruction word (VLIW)microprocessor, or other processing device. The processor also may beimplemented by a controller, a microcontroller, an application specificintegrated circuit (ASIC), a field programmable gate array (FPGA), aprogrammable logic device (PLD), and so forth.

In various aspects, the processor may be arranged to run an operatingsystem (OS) and various applications. Examples of an OS comprise, forexample, operating systems generally known under the trade name of AppleOS, Microsoft Windows OS, Android OS, and any other proprietary or opensource OS.

In some embodiments, at least one non-transitory computer-readablestorage medium is provided having computer-executable instructionsembodied thereon, wherein, when executed by at least one processor, thecomputer-executable instructions cause the at least one processor toperform embodiments of the methods described herein. Thiscomputer-readable storage medium can be embodied in the memory.

In some embodiments, the memory may comprise any machine-readable orcomputer-readable media capable of storing data, including bothvolatile/non-volatile memory and removable/non-removable memory. Thememory may comprise at least one non-volatile memory unit. Thenon-volatile memory unit is capable of storing one or more softwareprograms. The software programs may contain, for example, applications,user data, device data, and/or configuration data, or combinationstherefore, to name only a few. The software programs may containinstructions executable by the various components of the controller 120of the system 100.

For example, memory may comprise read-only memory (ROM), random-accessmemory (RAM), dynamic RAM (DRAM), Double-Data-Rate DRAM (DDR-RAM),synchronous DRAM (SDRAM), static RAM (SRAM), programmable ROM (PROM),erasable programmable ROM (EPROM), electrically erasable programmableROM (EEPROM), flash memory (e.g., NOR or NAND flash memory), contentaddressable memory (CAM), polymer memory (e.g., ferroelectric polymermemory), phase-change memory (e.g., ovonic memory), ferroelectricmemory, silicon-oxide-nitride-oxide-silicon (SONOS) memory, disk memory(e.g., floppy disk, hard drive, optical disk, magnetic disk), or card(e.g., magnetic card, optical card), or any other type of media suitablefor storing information.

In one embodiment, the memory may contain an instruction set, in theform of a file for executing a method of generating one or more timinglibraries as described herein. The instruction set may be stored in anyacceptable form of machine-readable instructions, including source codeor various appropriate programming languages. Some examples ofprogramming languages that may be used to store the instruction setcomprise, but are not limited to: Java, C, C++, C#, Python, Objective-C,Visual Basic, or .NET programming. In some embodiments a compiler orinterpreter is comprised to convert the instruction set into machineexecutable code for execution by the processor.

In some embodiments, the I/O interface may comprise any suitablemechanism or component to at least enable a user to provide input (i.e.,configuration parameters, etc.) to the controller 120 and the controller120 to provide output control to the other components of the system 100(e.g., pump, motor, etc.).

FIG. 2 is a flowchart illustrating a method 200 of fabricating asemiconductor structure, in accordance with some embodiments of thepresent disclosure. FIG. 3A through 3F are cross-sectional views of asemiconductor structure 300 at various fabrication stages, constructedin accordance with some embodiments, The method 200 is described belowin conjunction with FIG. 2 and FIGS. 3A through 3F wherein thesemiconductor structure 300 is fabricated by using embodiments of themethod 200. It is understood that additional steps can be providedbefore, during, and after the method 200, and some of the stepsdescribed below can be replaced or eliminated, for additionalembodiments of the method. It is further understood that additionalfeatures can be added in the semiconductor structure 300, and some ofthe features described below can be replaced or eliminated, foradditional embodiments of the semiconductor structure 300.

The semiconductor structure 300 may be an intermediate structure duringthe fabrication of an IC, or a portion thereof. The IC may include logiccircuits, memory structures, passive components (such as resistors,capacitors, and inductors), and active components such as diodes,field-effect transistors (FETs), metal-oxide semiconductor field effecttransistors (MOSFETs) , complementary metal-oxide semiconductor (CMOS)transistors, bipolar transistors, high voltage transistors, highfrequency transistors, fin-like FETs (FinFETs), other three-dimensional(3D) FETs, and combinations thereof. The semiconductor structure 300 mayinclude a plurality of semiconductor devices (e.g., transistors), whichmay be interconnected.

Referring to FIGS. 2 and 3A, the method 200 includes operation 202, inwhich a substrate 302 is provided in a semiconductor machine, inaccordance with some embodiments. The semiconductor machine is, forexample, a spin coater system 100 of FIG. 1 . FIG. 1A is across-sectional view of a semiconductor structure 300 including thesubstrate 302, in accordance with some embodiments.

In some embodiments, the substrate 302 may be a bulk semiconductorsubstrate including one or more semiconductor materials. In someembodiments, the substrate 302 may include silicon, silicon germanium,carbon doped silicon (Si:C), silicon germanium carbide, or othersuitable semiconductor materials. In some embodiments, the substrate 302is composed entirely of silicon.

In some embodiments, the substrate 302 may include one or more epitaxiallayers formed on a top surface of a bulk semiconductor substrate. Insome embodiments, the one or more epitaxial layers introduce strains inthe substrate 302 for performance enhancement. For example, theepitaxial layer includes a semiconductor material different from that ofthe bulk semiconductor substrate, such as a layer of silicon germaniumoverlying bulk silicon or a layer of silicon overlying bulk silicongeranium. In some embodiments, the epitaxial layer(s) incorporated inthe substrate 302 are formed by selective epitaxial growth, such as, forexample, metalorganic vapor phase epitaxy (MOVPE), molecular beamepitaxy (MBE), hydride vapor phase epitaxy (HYPE), liquid phase epitaxy(LPE), metal-organic molecular beam epitaxy (MOMBE), or combinationsthereof.

In some embodiments, the substrate 302 may be asemiconductor-on-insulator (SOI) substrate. In some embodiments, the SOIsubstrate includes a semiconductor layer, such as a silicon layer formedon an insulator layer. In some embodiments, the insulator layer is aburied oxide (BOX) layer including silicon oxide or silicon germaniumoxide. The insulator layer is provided on a handle substrate such as,for example, a silicon substrate. In some embodiments, the SOI substrateis formed using separation by implanted oxygen (SIMOX) or other suitabletechnique, such as wafer bonding and grinding.

In some embodiments, the substrate 302 may also include a dielectricsubstrate such as silicon oxide, silicon nitride, silicon oxynitride, alow-k dielectric, silicon carbide, and/or other suitable layers.

In some embodiments, the substrate 302 may also include various p-typedoped regions and/or n-type doped regions, implemented by a process suchas ion implantation and/or diffusion. Those doped regions includen-well, p-well, lightly doped region (LDD) and various channel dopingprofiles configured to form various IC devices, such as a COMOStransistor, imaging sensor, and/or light emitting diode (LED). Thesubstrate 302 may further include other functional features such as aresistor and/or a capacitor formed in and/or on the substrate 302.

In some embodiments, the substrate 302 may also include variousisolation features. The isolation features separate various deviceregions in the substrate 302. The isolation features include differentstructures formed by using different processing technologies. Forexample, the isolation features may include shallow trench isolation(STI) features. The formation of an STI may include etching a trench inthe substrate 302 and filling in the trench with insulator materialssuch as silicon oxide, silicon nitride, and/or silicon oxynitride. Thefilled trench may have a multi-layer structure such as a thermal oxideliner layer with silicon nitride filling the trench. A chemicalmechanical polishing (CMP) may be performed to polish back excessiveinsulator materials and planarize the top surface of the isolationfeatures.

In some embodiments, the substrate 302 may also include gate stacksformed by dielectric layers and electrode layers. The dielectric layersmay include an interfacial layer and a high-k dielectric layer depositedby suitable techniques, such as chemical vapor deposition (CVD), atomiclayer deposition (ALD), physical vapor deposition (PVD), thermaloxidation, combinations thereof, and/or other suitable techniques. Theinterfacial layer may include silicon dioxide and the high-k dielectriclayer may include LaO, A10, ZrO, TiO, Ta₂O₅, Y₂O₃, SrTiO₃, BaTiO₃,BaZrO, HfZrO, HfLaO, HfSiO, LaSiO, AlSiO, HfTa0, HfSiO, (Ba,Sr)TiO₃(BST), Al₂O₃, Si₃N₄, SiON, and/or other suitable materials. Theelectrode layer may include a single layer or alternatively amulti-layer structure, such as various combinations of a metal layerwith a work function to enhance the device performance (work functionmetal layer), liner layer, wetting layer, adhesion layer and aconductive layer of metal, metal alloy or metal silicide). The electrodelayer may include Ti, Ag, Al, TiAlN, TaC, TaCN, TaSiN, Mn, Zr, TiN, TaN,Ru, Mo, Al, WN, Cu, W, any suitable materials, and/or a combinationthereof.

In some embodiments, the substrate 302 may also include a plurality ofinter-level dielectric (ILD) layers and conductive features integratedto form an interconnect structure configured to couple the variousp-type and n-type doped regions and the other functional features (suchas gate electrodes), resulting in a functional integrated circuit. Inone example, the substrate 302 may include a portion of the interconnectstructure and the interconnect structure may include a multi-layerinterconnect (MLI) structure and an ILD layer integrated with a MLIstructure, providing an electrical routing to couple various devices inthe substrate 302 to the input/output power and signals. Theinterconnect structure includes various metal lines, contacts and viafeatures (or via plugs). The metal lines provide horizontal electricalrouting. The contacts provide vertical connection between siliconsubstrate and metal lines while via features provide vertical connectionbetween metal lines in different metal layers.

In some embodiments, the substrate 302 may include a material layer 304that can be patterned by the method 200 and as such may also be referredto as a pattentable layer. In some embodiments, the material layer 304serves as a hard mask layer including material(s) such as silicon oxide,silicon nitride, silicon oxynitride, or titanium nitride. In someembodiments, the material layer 304 severs as anti-reflection coatinglayer including nitrogen-free material(s) such as silicon oxide, siliconoxygen carbide, or plasma enhanced chemical vapor deposited siliconoxide. In some embodiments, the material layer 304 is formed by adeposition process such as, for example, chemical vapor deposition(CVD), physical vapor deposition (PVD), or plasma enhanced chemicalvapor deposition (PECVD). The material layer 304 is optional and isomitted in some embodiments.

Referring to FIGS. 2 and 3B, the method 200 proceeds to operation 204,in which a RRC composition is applied to the surface of the substrate302 (e.g., the surface of the material layer 304) to form a RRC layer306, in accordance with some embodiments. FIG. 3B is a cross-sectionalview of the structure 300 after applying the RRC composition to thesurface of the substrate 302 to form the RRC layer 306, in accordancewith some embodiments. .

As discussed above, the RRC composition includes an organic solventhaving Hansen solubility parameters in specific ranges and an acid or abase. The RRC composition is configured to moisten a surface of thesubstrate 302 for diminishing the surface tension between thephotoresist and the surface of the substrate 302. As a result, thephotoresist consumption is reduced and the thickness uniformity of thephotoresist coating is enhanced. Various additives such as chelatingagent, surfactant, aqueous solvent, high boing point solvent, and/orwater are added as discussed above to further improve the efficacy ofRRC composition in reducing the photoresist consumption and improvingthe thickness uniformity of the photoresist coating.

In some embodiments, the RRC composition is dispersed through a nozzle(e.g., nozzle 108 of FIG. 1 ) to the surface of the substrate 302 at asuitable flow rate and at a predetermined amount. In some embodiments,the RRC composition is dispersed at a flow rate between 5 standard cubiccentimeters per minute (sccm) and about 30 sccm. In some embodiments,the RRC composition is dispersed while the substrate 302 is spinning. Insome embodiments, the spinning speed is in the range from 1500revolutions per minute (rpm) to 3500 rpm so that the RRC layer 306 canbe spread out evenly over the surface of the substrate to provide theRRC layer 306 with a uniform thickness. In some embodiments, the RRCcomposition is dispensed while the substrate 302 is in the static state(i.e., not spinning). After dispensing the RRC composition, thesubstrate 302 is spanned so that the RRC composition can be spread outevenly over the entire surface of the substrate 302 to obtain the RRClayer 306 with a uniform thickness. In some embodiments, the substrate302 can be spanned at a spin speed ranging from 50 revolutions perminute (rpm) to 1500 rpm for a period of 1 second to 20 seconds.

Referring to FIGS. 2 and 3C, the method 200 proceeds to operation 206,in which a photoresist layer 310 is formed over the RRC layer 306, inaccordance with some embodiments. FIG. 3C is a cross-sectional view ofthe structure 300 after forming the photoresist layer 310 over the RRClayer 306, in accordance with some embodiments. .

The photoresist layer 310 is sensitive to radiation used in alithography exposure process and has a resistance to etch (orimplantation). In some embodiments, the photoresist layer 310 issensitive to a radiation, such as I-line light, a DUV light (e.g., 248nm radiation by krypton fluoride (KrF) excimer laser or 193 nm radiationby argon fluoride (ArF) excimer laser, an EUV light (e.g., 13.5 nmlight), an electron beam (e-beam), and an ion beam. In the presentembodiment, the photoresist layer 310 is sensitive to EUV radiation.

As discussed above, photon absorption has been a problem in EUVlithography if conventional organic photoresist is used. Therefore,metal-containing photoresists are used in the present disclosure. Insome embodiments, the photoresist layer 310 includes a metal-containingmaterial, a polymeric material as a matrix that is resistive to etch (orimplantation), radiation-sensitive component (such as photo-acidgenerator (PAG)) that is reactive to the polymeric material, a quencherbase, and a chromophore.

In some embodiments, the metal-containing material of the photoresistlayer 310 includes one or more metallic elements, such as cesium (Cs),barium (Ba), lanthanum (La), indium (In), cerium (Ce), silver (Ag), ortin (Sn), or combinations thereof

In some embodiments, the metal-containing material includes metal oxidenanoparticles. In some embodiments, the photoresist layer 310 includesone or more metal oxides nanoparticles selected from the groupconsisting of titanium dioxide, zinc oxide, zirconium dioxide, nickeloxide, cobalt oxide, manganese oxide, copper oxides, iron oxides,strontium titanate, tungsten oxides, vanadium oxides, chromium oxides,tin oxides, hafnium oxide, indium oxide, cadmium oxide, molybdenumoxide, tantalum oxides, niobium oxide, aluminum oxide, and combinationsthereof. As used herein, nanoparticles are particles having an averageparticle size between about 1 nm and about 20 nm. Metal oxidenanoparticle sizes less than about 1 nm are difficult to obtain and usein photoresist compositions. Metal oxide nanoparticles greater thanabout 20 nm are too large for use in a resist in embodiments of thedisclosure. In some embodiments, the metal oxide nanoparticles have anaverage particle size between about 2 and about 5 nm. In someembodiments, the amount of metal oxide nanoparticles in the photoresistcomposition ranges from about 1 wt. % to about 15 wt. % based on theweight of the solvent for the photoresist composition. In someembodiments, the amount of nanoparticles in the photoresist compositionranges from about 2 wt. % to about 10 wt. % based on the weight of thesolvent for the photoresist composition. Concentrations of the metaloxide nanoparticles less than about 1 wt. % provide a photoresistcoating that is too thin. Concentrations of the metal oxidenanoparticles greater than about 15 wt. % will provide a photoresistcomposition that is too viscous and that will be difficult to provide aphotoresist coating of uniform thickness on the substrate 302.

In some embodiments, the metal oxide nanoparticles are complexed with aligand. In some embodiments, the ligand is a carboxylic acid or sulfonicacid ligand. For example, in some embodiments, zirconium oxide orhafnium oxide nanoparticles are complexed with methacrylic acid forminghafnium methacrylic acid (HfMAA) or zirconium methacrylic acid (ZrMAA).In some embodiments, the metal oxide nanoparticles are complexed withligands including aliphatic or aromatic groups. The aliphatic oraromatic groups may be unbranched or branched with cyclic or noncyclicsaturated pendant groups containing 1-9 carbons, including alkyl groups,alkenyl groups, and phenyl groups. The branched groups may be furthersubstituted with oxygen or halogen. In some embodiments, the ligandconcentration is about 10 wt. % to about 40 wt. % based on the weight onthe metal oxide nanoparticles. At concentrations of the ligand belowabout 10 wt. % the concentration of the ligand is insufficient tocomplex the metal oxide nanoparticles. Concentrations of the ligandabove about 40 wt. % do not provide a significant improvement incomplexing the metal oxide nanoparticles over concentrations of theligand at about 40 wt.

In some embodiments, the metal oxide/ligand complexes are formed of acluster including metallic core having a metal with high EUV absorption,such as Cs, Ba, La, Ce, In, Sn, Ag, or Sb combined with oxygen and/ornitrogen to form 1 to 12 metal core-clusters. The metallic core-clustersare complexed with ligands including aliphatic or aromatic groups. Thealiphatic or aromatic groups may be unbranched or branched with cyclicor noncyclic saturated pendant groups containing 1-9 carbons, includingalkyl groups, alkenyl groups, and phenyl groups. The branched groups maybe further substituted with oxygen or halogen in some embodiments.

Examples of suitable metal oxide/ligand complexes according toembodiments of the disclosure are:

The photoresist layer 310 is formed by spin coating process in someembodiments. In some embodiments, the photoresist layer 310 is furthertreated with a soft baking process to drive off the solvent. In someembodiments, the soft bake process is performed at a temperaturesuitable to evaporate the solvent in the photoresist layer 310, such asbetween about 100° C. and 200° C., although the precise temperaturedepends upon the materials chosen for the photoresist layer 310. Forexample, in some embodiments, the photoresist layer 310 is heated toabout 150° C. The soft bake process is performed for a time sufficientto cure and dry the photoresist layer 310. In some embodiments, the softbake process is performed for a time period from about 10 seconds toabout 10 minutes. For example, in some embodiments, the photoresistlayer 310 is cured for about 300 seconds.

Referring to FIGS. 2 and 3D, the method 200 proceeds to operation 208,in which the photoresist layer 310 is exposed to a patterning radiation320, in accordance with some embodiments. FIG. 3D is a cross-sectionalview of the structure 300 after exposing the photoresist layer 310 tothe patterning radiation 320, in accordance with some embodiments.

In some embodiments, the photoresist layer 310 is exposed to thepatterning radiation 320 from a light source through a photomask 330.The photomask 330 has a predefined pattern designed for an IC, based ona specification of the IC to be manufactured. The patterns of thephotomask 330 correspond to patterns of materials that make up thevarious components of the IC device to be fabricated. For example, aportion of the IC design layout includes various IC features, such as anactive region, gate electrode, source and drain, metal lines or vias ofan interlayer interconnection, and openings for bonding pads, to beformed in the substrate 302 and/or the material layer 304 disposed onthe substrate 302.

The photomask 330 includes first regions 332 and second regions 334. Inthe first regions 332, the patterning radiation 320 is blocked by thephotomask 330 to reach the photoresist layer 310, while in the secondregions 334, the patterning radiation 320 is not blocked by thephotomask 330 and can pass through the photomask 330 to reach thephotoresist layer 310. As a result, portions of the photoresist layer310 below the second regions 334 receive the patterning radiation 320,referred to as exposed portions. While portions of the photoresist layer310 below the first regions 332 do not receive the patterning radiation320, referred to as unexposed portions.

In some embodiments, the patterning radiation 320 is an EUV radiation(e.g., 13.5 nm). Alternatively, in some embodiments, the patterningradiation 320 is a DUV radiation (e.g., from a 248 nm KrF excimer laseror a 193 nm ArF excimer laser), X-ray radiation, an e-beam radiation, anion beam radiation, or other suitable radiations. In some embodiments,operation 208 is performed in a liquid (immersion lithography) or in avacuum for EUV lithography and e-beam lithography.

Subsequently, the photoresist layer 310 may be subjected to apost-exposure bake process. The post-exposure bake process may beperformed at a temperature from about 50° C. to about 150° C. for aduration from about 60 seconds to about 360 seconds.

Referring to FIGS. 2 and 3E, the method 200 proceeds to operation 210,in which the photoresist layer 310 is developed using a developer toform a patterned photoresist layer 310P, in accordance with someembodiments. FIG. 2E is a cross-sectional view of the structure 300after forming the patterned photoresist layer 310P, in accordance withsome embodiments.

Referring to FIG. 2E, during the developing process, the developer isapplied to the photoresist layer 310. The developer may remove theexposed or unexposed portions of the photoresist layer 310 depending onthe resist type. For example, and as shown in FIG. 2E, the photoresistlayer 310 includes a negative tone resist, so the portions of thephotoresist layer 310 that are exposed by the patterning radiation 320are not dissolved by the developer and remain in the structure 300. Onthe other hand, if the photoresist layer 310 includes a positive toneresist, the portions of the photoresist layer 310 that are exposed bythe patterning radiation 320 would be dissolved by the developer,leaving the unexposed portions in the structure 300.

The developer may include alcohols, aromatic hydrocarbons, and the like.Examples of alcohols include, but are not limited to, methanol, ethanol,1-butanol, and 4-Methyl-2-pentanol. Examples of aromatic hydrocarbonsinclude, but are not limited to, xylene, toluene and benzene. In someembodiments, the developer is selected from at least one of methanol,4-methyl-2-pentanol and xylene.

The developer may be applied using any suitable methods. In someembodiments, the developer is applied by dipping the structure into adeveloper bath. In some embodiments, the developing solution is sprayedonto the photoresist layer 310.

In the present disclosure, by using the RRC composition to treat thesurface of the substrate 302 so to improve the thickness uniformity ofthe photoresist layer 310, the performance of the metal-containingphotoresist is greatly enhanced with the LWR being improved greater thanabout 3%, the expose energy being reduced greater than about 3%, anddefect counts being reduced greater than 5%. Consequently, thephotoresist pattern can be transferred to the underlying layer at a highprecision.

Referring to FIGS. 2 and 3F, the method 200 proceeds to operation 212,in which the material layer 304 is etched using the patternedphotoresist layer 310P as an etch mask, in accordance with someembodiments. FIG. 2F is a cross-sectional view of the structure 300after etching the material layer 304 using the patterned photoresistlayer 310P as an etch mask, in accordance with some embodiments.

Referring to FIG. 2F, the material layer 304 is patterned, using thepatterned photoresist layer 310P as an etch mask, to form a patternedmaterial layer 304P.

An etching process may be performed to transfer the pattern in thepatterned photoresist layer 310P to the material layer 304. In someembodiments, the etching process employed is an anisotropic etch such asa dry etch although any suitable etch process may be utilized. In someembodiments, the dry etch is a reactive ion etch (ME) or a plasma etch.In some embodiments, the dry etch is implemented by fluorine-containinggas (e.g., CF₄, SF₆, CH₂F₂, CHF₃, and/or C₂F6), chlorine-containing gas(e.g., Cl₂, CHCl₃, CCl₄, and/or BCl₃), bromine-containing gas (e.g., HBrand/or CHBr₃), oxygen-containing gas, iodine-containing gas, othersuitable gases and/or plasmas, or combinations thereof. In someembodiments, an oxygen plasma is performed to etch the material layer304. In some embodiments, the anisotropic etch is performed at atemperature from about 250° C. to 450° C. for a duration from about 20seconds to about 300 seconds.

If not completely consumed in the etching process, after formation ofthe patterned material layer 304P, the patterned photoresist layer 310Pis removed, for example, by plasma ashing or wet stripping.

One aspect of this description relates to a method for reducing resistconsumption (RRC). The method includes treating a surface of a substrateusing a RRC composition and forming a photoresist layer comprising ametal-containing material on the RRC composition treated surface. TheRRC composition includes a first solvent and an acid or a base. Thefirst solvent has a dispersion parameter between 10 and 25. The acid hasan acid dissociation constant between −20 and 6.8. The base having anacid dissociation constant between 7.2 and 45.

Another aspect of this description relates to a method for forming asemiconductor structure. The method includes depositing a material layerover a substrate, forming a layer of a reducing resist consumption (RRC)composition on the material layer, forming a photoresist layercomprising a metal-containing material on the RRC composition layer,patterning the photoresist layer to form a patterned photoresist layer,and etching the material layer using the patterned photoresist layer asan etch mask. The RRC composition includes a solvent and an acid or abase. The solvent has the following Hansen solubility parameters: adispersion parameter between 10 and 25, a polarity parameter between 3and 25, and a hydrogen bonding parameter between 4 and 30. The acid hasan acid dissociation constant between −20 and 6.8. The base has an aciddissociation constant between 7.2 and 45.

Still another aspect of this description relates to a method for forminga semiconductor structure. The method includes depositing a materiallayer over a substrate, forming a layer of a reducing resist consumption(RRC) composition on the material layer. forming a photoresist layercomprising a metal-containing material on the RRC composition layer,exposing the photoresist layer to an extreme ultraviolet (EUV) radiationto form a patterned photoresist layer, and etching the material layerusing the patterned photoresist layer as an etch mask. The RRCcomposition includes a first solvent having a hydrogen bonding parameterbetween 4 and 30, an acid having an acid dissociation constant between−20 and 6.8 or a base having an acid dissociation constant between 7.2and 45, a chelating agent, a surfactant, a second solvent having aboiling point greater than 150° C., and an aqueous solvent or water.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method for reducing resist consumption (RRC),comprising: treating a surface of a substrate using a RRC composition;and forming a photoresist layer comprising a metal-containing materialon the RRC composition treated surface, wherein the RRC compositioncomprises: a first solvent having a dispersion parameter between 10 and25; and an acid having an acid dissociation constant between −20 and6.8, or a base having an acid dissociation constant between 7.2 and 45.2. The method of claim 1, wherein the first solvent comprises propyleneglycol methyl ether (PGME), propylene glycol ethyl ether (PGEE),y-butyrolactone, cyclohexanone, ethyl lactate, methyl isobutyl carbinol,propylene glycol monomethyl ether acetate, methanol, ethanol, propanol,n-butanol, acetone, dimethylfuran, acetonitrile, isopropyl alcohol,tetrahydrofuran, acetic acid, diacetone alcohol or combinations thereof.3. The method of claim 1, wherein the first solvent has a polarityparameter between 3 and 25 and a hydrogen bonding parameter between 4and
 30. 4. The method of claim 3, wherein a concentration of the acid orbase ranges from 0.1 wt. % to 20 wt. % based on a total weight of theRRC composition.
 5. The method of claim 1, wherein the acid is anorganic acid comprising ethanedioic acid, methanoic acid,2-hydroxypropanoic acid, 2-hydroxybutanedioic acid, citric acid, uricacid, trifluoromethanesulfonic acid, benzenesulfonic acid,ethanesulfonic acid, methanesulfonic acid, acetic acid, oxalic acid,maleic acid or combinations thereof, or an inorganic acid including, butnot limited to, nitric acid (HNO₃), sulfuric acid (H₂SO₄), hydrochloricacid (HCl), hydrobromic acid (HBr), phosphoric acid (H₃PO₄) orcombinations thereof.
 6. The method of claim 1, wherein the base is anorganic base comprising monoethanolamine, monoisopropanolamine,2-amino-2-methyl-1-propanol, 1H-benzotriazole, 1,2,4-triazole,1,8-diazabicycloundec-7-ene, 1,5-diazabicyclo[4.3.0]non-5-ene orcombinations thereof, or an inorganic base comprising ammonia (NH₃),ammonium hydroxide, ammonium sulfamate, ammonium carbamate, sodiumhydroxide (NaOH), potassium hydroxide (KOH) or combinations thereof. 7.The method of claim 1, wherein the RRC composition further comprises achelating agent.
 8. The method of claim 7, wherein the chelating agentcomprises ethylenediaminetetraacetic acid(EDTA),ethylenediamine-N,N′-disuccinic acid (EDDS),diethylenetriaminepentaacetic acid (DTPA), polyaspartic acid,trans-1,2-cyclohexanediamine-N,N,N′,N′-tetraacetic acid monohydrate,ethylenediamine or combinations thereof.
 9. The method of claim 1,wherein the RRC composition further comprises a surfactant.
 10. Themethod of claim 1, wherein the RRC composition further comprises asecond solvent having a boiling point greater than 150° C.
 11. Themethod of claim 1, wherein the RRC composition further comprises anaqueous solvent.
 12. The method of claim 1, wherein the RRC compositionfurther comprises water.
 13. A method for forming a semiconductorstructure, comprising: depositing a material layer over a substrate;forming a layer of a reducing resist consumption (RRC) composition onthe material layer; forming a photoresist layer comprising ametal-containing material on the RRC composition layer; patterning thephotoresist layer to form a patterned photoresist layer; and etching thematerial layer using the patterned photoresist layer as an etch mask,wherein the RRC composition comprises: a solvent having the followingHansen solubility parameters: a dispersion parameter between 10 and 25,a polarity parameter between 3 and 25, and a hydrogen bonding parameterbetween 4 and 30; and an acid having an acid dissociation constantbetween −20 and 6.8, or a base having an acid dissociation constantbetween 7.2 and
 45. 14. The method of claim 13, wherein the solventcomprises propylene glycol methyl ether (PGME), propylene glycol ethylether (PGEE), y-butyrolactone, cyclohexanone, ethyl lactate, methylisobutyl carbinol, propylene glycol monomethyl ether acetate, methanol,ethanol, propanol, n-butanol, acetone, dimethylfuran, acetonitrile,isopropyl alcohol, tetrahydrofuran, acetic acid, diacetone alcohol orcombinations thereof.
 15. The method of claim 13, wherein the acid is anorganic acid comprising ethanedioic acid, methanoic acid,2-hydroxypropanoic acid, 2-hydroxybutanedioic acid, citric acid, uricacid, trifluoromethanesulfonic acid, benzenesulfonic acid,ethanesulfonic acid, methanesulfonic acid, acetic acid, oxalic acid,maleic acid or combinations thereof, or an aqueous acid comprisingH₂SO₄, HNO₃, HCl, H₃PO₄, CCl₃COOH, HBr or combinations thereof.
 16. Themethod of claim 13, wherein the base is an organic base comprisingmonoethanolamine, monoisopropanolamine, 2-amino-2-methyl-1-propanol,1H-benzotriazole, 1,2,4-triazole, 1,8-diazabicycloundec-7-ene,1,5-diazabicyclo[4.3.0]non-5-ene or combinations thereof, or an aqueousbase comprising NaOH, NH₃, KOH, TMAH, TEAH or combinations thereof. 17.The method of claim 13, wherein patterning the photoresist layercomprises: exposing the photoresist layer to an extreme ultraviolet(EUV) radiation; and developing the exposed photoresist layer.
 18. Amethod for forming a semiconductor structure, comprising: depositing amaterial layer over a substrate; forming a layer of a reducing resistconsumption (RRC) composition on the material layer; forming aphotoresist layer comprising a metal-containing material on the RRCcomposition layer; exposing the photoresist layer to an extremeultraviolet (EUV) radiation to form a patterned photoresist layer; andetching the material layer using the patterned photoresist layer as anetch mask, wherein the RRC composition comprises: a first solvent havinga hydrogen bonding parameter between 4 and 30; an acid having an aciddissociation constant between −20 and 6.8, or a base having an aciddissociation constant between 7.2 and 45; a chelating agent; asurfactant; a second solvent having a boiling point greater than 150°C.; and an aqueous solvent, or water.
 19. The method of claim 18,wherein the first solvent comprises propylene glycol methyl ether(PGME), propylene glycol ethyl ether (PGEE), γ-butyrolactone,cyclohexanone, ethyl lactate, methyl isobutyl carbinol, propylene glycolmonomethyl ether acetate, methanol, ethanol, propanol, n-butanol,acetone, dimethylfuran, acetonitrile, isopropyl alcohol,tetrahydrofuran, acetic acid, diacetone alcohol or combinations thereof.20. The method of claim 18, wherein the second solvent comprises CHAX,dipropylene glycol dimethyl ether (DMM), propylene glycol diacetate(PGDA), dipropylene glycol methyl n-propyl ether (DPMNP), dipropyleneglycol methyl ether acetate (DPMA), 1,4-butanediol diacrylate(1,4-BDDA), 1,3-butanediol di acetate (1,3-BGDA), 1,6-hexanedioldiacrylate (1,6-HDDA), tripropylene glycol monomethyl ether (TPM),1,3-propanediol, propylene glycol,1-methoxy-2-(2-propoxypropoxy)propane, hexane-1,6-diyl diacetate,butane-1,4-diyl diacetate, propane-1,2-diyl diacetate,2-methoxy-1-((1-methoxypropan-2-yl)oxy)propane,1-((1-methoxypropan-2-yl)oxy)propan-2-yl acetate, butane-1,2,4-triol,2-(2-(2-methoxypropoxy)propoxy)propan-1-ol, and combinations thereof.